U.S. patent application number 10/850648 was filed with the patent office on 2005-11-24 for magnetic focus rings for improved copper plating.
Invention is credited to Berman, Michael J., Reder, Steven E..
Application Number | 20050258044 10/850648 |
Document ID | / |
Family ID | 35374140 |
Filed Date | 2005-11-24 |
United States Patent
Application |
20050258044 |
Kind Code |
A1 |
Berman, Michael J. ; et
al. |
November 24, 2005 |
Magnetic focus rings for improved copper plating
Abstract
A method and system wherein magnets are employed on the outside
of a plating bath chamber to control the field lines that are used
during the plating process. By being able to control the field
lines during the plating process, improved gap fill and uniformity
can be achieved. The magnetic field acting on the bath can be
continuous, pulsed, stressed (i.e., the shape of the field can be
changed), sinusoidal, etc. The magnetic field can be modulated as
function of time to produce a desired copper uniformity on the
wafer. It is anticipated that there is no limit to how the shape of
the magnets or magnetic field can be configured and controlled to
achieve the desired result for both fill of deep contacts and the
uniformity needed to match the succeeding polishing process.
Inventors: |
Berman, Michael J.; (West
Linn, OR) ; Reder, Steven E.; (Boring, OR) |
Correspondence
Address: |
LSI LOGIC CORPORATION
1621 BARBER LANE
MS: D-106
MILPITAS
CA
95035
US
|
Family ID: |
35374140 |
Appl. No.: |
10/850648 |
Filed: |
May 21, 2004 |
Current U.S.
Class: |
205/89 ;
257/E21.175; 257/E21.585 |
Current CPC
Class: |
C25D 5/006 20130101;
H01L 21/2885 20130101; H01L 21/76877 20130101; C25D 5/18 20130101;
C25D 7/123 20130101; C25D 5/00 20130101; C25D 21/12 20130101 |
Class at
Publication: |
205/089 |
International
Class: |
C25D 005/00 |
Claims
What is claimed is:
1. A method for using an anode to plate a cathode with ions in a
bath chamber, comprising: applying a voltage to the anode and the
cathode, the anode and cathode being disposed in the bath chamber,
thereby causing ions to flow along field lines from the anode to
the cathode in the bath chamber and plate the cathode; and using at
least one magnet to adjust the field lines.
2. A method as recited in claim 1, wherein the anode comprises
copper and the cathode comprises a wafer.
3. A method as recited in claim 1, wherein the step of using at
least one magnet to adjust the field lines comprises using a
plurality of permanent magnets.
4. A method as recited in claim 1, wherein the step of using at
least one magnet to adjust the field lines comprises using a
plurality of electro-magnets.
5. A method as recited in claim 1, wherein the step of using at
least one magnet to adjust the field lines comprises using a
control system and a plurality of electro-magnets connected to the
control system.
6. A method as recited in claim 1, wherein the step of using at
least one magnet to adjust the field lines comprises using a
plurality of magnets which are disposed outside of the bath
chamber.
7. A method as recited in claim 1, wherein the step of using at
least one magnet to adjust the field lines comprises using a
plurality of magnets which are disposed outside of the bath
chamber, around a circumference of the bath chamber.
8. A method as recited in claim 1, wherein the step of using at
least one magnet to adjust the field lines comprises using a
plurality of magnets and controlling the magnets such that the
magnets provide a magnetic field which is at least one of
continuous, pulsed, stressed and sinusoidal.
9. A method as recited in claim 1, wherein the step of using at
least one magnet to adjust the field lines comprises using a
plurality of magnets and controlling the magnets such that the
magnets provide a magnetic field which is modulated over time.
10. A plating system comprising: a bath chamber; an anode disposed
in the bath chamber; a cathode disposed in the bath chamber; a
voltage source connected to the anode and cathode, wherein
application of voltage causes ions to flow along field lines from
the anode to the cathode in the bath chamber and plate the cathode;
and at least one magnet disposed proximate the bath chamber,
wherein said at least one magnet adjusts the field lines.
11. A system as recited in claim 10, wherein the anode comprises
copper and the cathode comprises a wafer.
12. A system as recited in claim 10, wherein said at least one
magnet comprises a plurality of permanent magnets.
13. A system as recited in claim 10, wherein said at least one
magnet comprises a plurality of electro-magnets.
14. A system as recited in claim 13, further comprising a control
system connected to the plurality of electro-magnets.
15. A system as recited in claim 10, wherein said at least one
magnet comprises a plurality of magnets which are disposed outside
of the bath chamber.
16. A system as recited in claim 10, wherein said at least one
magnet comprises a plurality of magnets which are disposed outside
of the bath chamber, around a circumference of the bath
chamber.
17. A system as recited in claim 14, wherein the control system is
configured to control the electro-magnets such that the
electro-magnets provide a magnetic field which is at least one of
continuous, pulsed, stressed and sinusoidal.
18. A system as recited in claim 14, wherein the control system is
configured to control the electro-magnets such that the
electro-magnets provide a magnetic field which is modulated over
time.
Description
BACKGROUND
[0001] The present invention generally relates to methods and
systems for depositing metal on a substrate, such as depositing
copper on a semiconductor wafer. The present invention more
specifically relates to the use of a magnetic filed, such as with
magnetic focus rings, to improve copper plating.
[0002] In the semiconductor industry, copper wire interconnects are
becoming the process of record for 0.13 micron processing node and
smaller. The current technology used for this process is
electro-chemical-deposition (ECD). Many companies manufacture tools
for this process. The final copper uniformity of the deposition
needs to match the uniformity of the CMP process as much as
possible from center to edge before the wafer goes into the post
polishing process (either chemical mechanical polishing (CMP) or
electro-polishing). If the non-uniformity of the final film and
polishing processes are not matched, there are problems with the
devices. Another problem is gap fill. As dimensions get smaller,
technology is relying more on the chemistry to assist gap fill.
However, voids are still a major problem with regard to the new
technologies which are being used.
[0003] Typically, current tool designs are very similar to each
other, except for differences in the design of the plating cell
head which holds the wafer (and which operates as the cathode in
the plating process), the cell body (which is the bath tank for the
plating solution), and the anode (which is the source of the copper
ions which become deposited on the wafer). In the industry, tool
suppliers provide a plumbing, re-circulation, and filtration system
for supplying the electrolyte solution to the surface of the wafer
in the presence of an electric field. As shown in FIG. 1, a DC
source 10 is used to apply a field from a copper anode 12 to a
wafer (the cathode) 14 in a plating bath chamber 16, and Cu2+
copper ions follow field lines 18 to the surface 20 of the wafer
14. In attempts to control the uniformity, each of the vendors that
manufacture a tool for this process has designed a different cell
head, a different bath structure, and different anode
configurations. However, all of these designs still yield a level
of non-uniformity that must be dealt with in future processing
steps. Other attempts using different chemical formulations have
also been devised to deal with the problems of non-uniformity of
deposit and the presence of voids.
[0004] Generally, existing solutions have not solved the uniformity
and gap fill problems associated with deposition of copper on a
semiconductor wafer. In fact, some of the designs have introduced
additional problems that are difficult to eliminate, such as edge
particles caused by the contact ring, or bulk defects caused by the
chemistry.
OBJECTS AND SUMMARY
[0005] An object of an embodiment of the present invention is to
provide a method and system which can be used to deposit copper
uniformly onto a wafer.
[0006] Another object of an embodiment of the present invention is
to provide a method and system which deposits copper onto a wafer
such that there is no gap fill problem.
[0007] Briefly, and in accordance with at least one of the
foregoing objects, an embodiment of the present invention provides
a method and system wherein magnets are employed proximate, such as
on the outside of, a plating bath chamber to control the field
lines that are used during the plating process. By being able to
control the field lines during the plating process, improved gap
fill and uniformity can be achieved.
[0008] The magnetic field acting on the bath can be continuous,
pulsed, stressed (i.e., the shape of the field can be changed),
sinusoidal, etc. The magnetic field can be modulated as function of
time to produce a desired copper uniformity on the wafer. It is
anticipated that there is no limit to how the shape of the magnets
or magnetic field can be configured and controlled to achieve the
desired result for both fill of deep contacts and the uniformity
needed to match the subsequent polish process.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] The organization and manner of the structure and operation
of the invention, together with further objects and advantages
thereof, may best be understood by reference to the following
description, taken in connection with the accompanying drawing,
wherein:
[0010] FIG. 1 illustrates a prior art system for depositing copper
on the surface of a semiconductor wafer;
[0011] FIG. 2 illustrates a system for depositing copper on the
surface of a semiconductor wafer, wherein the system is in
accordance with an embodiment of the present invention;
[0012] FIG. 3 provides a top view, showing magnets positioned
around the circumference of the bath chamber;
[0013] FIG. 4 provides a flow chart of a method which can be used
in connection with the system shown in FIG. 2, wherein the method
is in accordance with an embodiment of the present invention.
DESCRIPTION
[0014] While the invention may be susceptible to embodiment in
different forms, there are shown in the drawings, and herein will
be described in detail, specific embodiments of the invention. The
present disclosure is to be considered an example of the principles
of the invention, and is not intended to limit the invention to
that which is illustrated and described herein.
[0015] FIG. 2 illustrates a system 30 for depositing copper on the
surface 20 of a semiconductor wafer 14, wherein the system 30 is in
accordance with an embodiment of the present invention. The system
30 provides that magnets 32 are positioned proximate a bath housing
16. While the magnets 32 may possibly be placed within the bath
housing 16 if properly insulated, as shown in FIG. 3 preferably the
magnets 32 are positioned on the outside of the bath housing 16,
around its circumference or outer perimeter 34. Regardless, the
magnets 32 are used to provide a magnetic field to improve
uniformity and gap fill. Specifically, a DC source 10 is used to
apply a field from a copper anode 12 to a wafer (the cathode) 14 in
a plating bath chamber 16, and Cu2+ copper ions follow field lines
40 to the surface 20 of the wafer 14. The magnets 32 are used to
effectively modify the field lines 40 so that they are more linear
between the anode (i.e., the copper) 12 and the cathode (i.e., the
wafer) 14 (i.e., compare the field lines 18 illustrated in FIG. 1
to the field lines 40 illustrated in FIG. 2).
[0016] The magnets 32 may be permanent magnets and/or controllable
electro-magnets. If at least some of the magnets 32 are
electro-magnets, a control system 42 is connected to the
electro-magnets and is operable to modulate the magnets to provide
a desired magnetic filed such that the filed lines 40 between the
anode 12 and cathode 14 are tuned as desired to improve both
uniformity of copper deposit and improve gap fill. The magnetic
field acting on the bath can be continuous, pulsed, stressed (i.e.
the shape of the field can be changed), sinusoidal, etc. There is
no limit to how the shape of the magnets or magnetic field can be
configured and controlled to achieve the desired result for both
fill of deep contacts and the uniformity needed to match the polish
process.
[0017] The typical uniformity problems seen on plated wafers
manifests itself as a bulls eye, center to edge pattern. By
modulating the intensity of the magnetic field, the shape and
intensity of the field lines produced by the power supply connected
to the cathode and anode can be altered to produce a desired
uniformity pattern on the wafer. The shapes of the magnetic field
can also be controlled such that the intensity can be modulated at
any area of the bath. The magnetic fields generated would force the
field lines to be vertical in both the center of the wafer and at
the edge of the bath allowing the migrating copper ions to arrive
at the surface of the wafer "more vertical" therefore more
successfully in filling the deep gaps in both the center of the
wafer and the edge of the wafer.
[0018] Preferably, the control system 42 is configured such that
the magnetic filed is modulated over time. Improved vertical
plating at the edge of the wafer is more important at the beginning
of the plating process. As the contacts fill, the high aspect ratio
decreases. As this happens, preferably the magnetic filed is
modulated so that the field lines are changed to go from "the best
fill" to the most desired uniformity to meet the needs of the
polish process.
[0019] The present invention provides that fixed or electrically
controlled magnets are used in association with a plating bath
chamber to control the field lines that are used during the plating
process. By controlling the field lines during the plating process,
improved gap fill and uniformity can be achieved. None of the
currently available electroplating tools on the market utilize such
a method of field line control for uniformity or gap fill
improvement.
[0020] FIG. 4 shows a flow chart of at least one embodiment of this
invention. Box 100 explains the basic electroplating process and
box 102 explains the improved copper deposition process by the
utilization of a controlled magnetic field to improve deposition
uniformity.
[0021] While embodiments of the present invention are shown and
described, it is envisioned that those skilled in the art may
devise various modifications of the present invention without
departing from the spirit and scope of the appended claims.
* * * * *